Telemetry and overlay tools

Two jobs get conflated here, and picking the wrong tool for the job is why people stall out. Telemetry analysis is post-session: you record a lap, overlay it against a faster one, and find the corner where you’re losing two tenths. Live overlays are in-race: a delta bar, a relative box, fuel and standings on screen while you drive. SimHub does neither analysis job well, despite getting recommended for both, because it isn’t an analyzer at all.

Telemetry analysis: finding the lost time

Garage 61 is free and it’s where most people should start. It auto-uploads every lap you turn in iRacing and lets you overlay your throttle, brake, steering, and driving line against thousands of other drivers’ laps on the same track and car. The reference pool is deep enough that there is almost always a faster lap in your car to compare against.

The catch is picking the right reference. Do not overlay against the absolute fastest hotlap on the board. That lap was likely set by a 5,000+ iRating driver in the coldest, grippiest practice conditions, sometimes on a different track layout. Garage 61 shows each driver’s iRating next to their lap. Pick someone 300 to 500 iRating above you, in race-like conditions, and the delta becomes something you can actually copy.

VRS (Virtual Racing School) layers a Driving Analyser, setup packs, and a Virtual Coach on top of the same idea. The free “Casual” tier gets you started; paid subscription tiers unlock the data packs (car setups plus reference telemetry per series) and the Virtual Coach features. The community advice is the same as Garage 61’s: compare to the VRS average lap, not the fastest, and match conditions and static weather.

MoTeC i2 Pro is the deep, free package, and it’s the one to use for setup work. iRacing exports .ld files that i2 reads, exposing logged channels like ride heights, tire temperatures, and suspension travel, which is what open-setup series actually need. The learning curve is steep, so reach for it after you’ve outgrown line-and-input comparison.

iRacing’s native recording writes .ibt files when you toggle telemetry in-sim. They pile up fast, gigabytes per week, so clear the folder or you’ll repeat the “just deleted 68GB” experience.

How to actually read a trace

Watch the line and distance delta first, not throttle and brake. One meter is roughly 3 feet; anything more than a meter off the reference line is losing time before inputs even enter the picture. A wider, smoother arc that carries speed beats a tighter line you have to scrub off.

Then read the brake-trace shape. A downforce or formula car gives a triangular trace: a near-vertical stab to peak pressure, then a diagonal trail-off as speed and downforce bleed away. A GT car gives a squarer trace: vertical to peak, a held plateau, then a release as you turn in. If your trace doesn’t trail off where the reference’s does, your trail-braking is the lost time.

Last, look at throttle application on exit. Earlier and more progressive to full throttle is the payoff for getting entry right.

Live overlays and HUD

RaceLab is the popular live overlay app: delta, relative, standings, input traces, fuel calc, spotter, and track map. The free tier covers the essentials; Pro runs about EUR 4.90/month for the configurable layouts. iOverlay is the competitor, once free and now paid, and plenty of people run both, using iOverlay for its free pieces and RaceLab where they want customization.

SimHub belongs here, not in analysis. It’s a dashboard, LED, bass-shaker, and motion engine that also renders on-screen overlays. It drives rev LEDs, button-box displays, and shaker effects, with a huge community library of dashes and overlays (the ABS-trace pedal overlay is a perennial favorite). It is free donationware and worth it on a wheel for the dash and shaker work, but it will not tell you where you lost a tenth.

iRacing itself already gives you the F3 relative black box (gap to the cars immediately ahead and behind), F2 fuel, and an on-screen delta. On delta during races: keep it if a glance helps you self-correct, turn it off if you find yourself driving the bar instead of the track.

Crew Chief

Crew Chief is a free spotter and race-engineer voice app. It reads fuel, gaps, flags, incidents, and pit windows aloud, so you keep your eyes on the track instead of the relative box. Pair it with a relative HUD and it’ll warn you about slower cars before you reach them.

Why fuel calculators go wrong

Fuel calculators, including iRacing’s auto-fuel and RaceLab’s, read your recent consumption and extrapolate. They go wrong when your recent laps aren’t representative: fuel-saving laps, a different stint length, or laps under yellow drag the average off. Run a few clean green-flag laps at race pace before trusting the number, then add a margin lap of fuel. The math is only as good as the laps you feed it.

What to actually start with

Build the free stack first: Garage 61 for analysis, Crew Chief for audio engineering, and iRacing’s native black boxes for live info. Add Trading Paints for car liveries while you’re at it. From there, add VRS or MoTeC i2 when you want deeper analysis, RaceLab when you want a configurable HUD, and SimHub when you’ve got a dash or shaker to drive. FFB-enhancement apps like MAIRA (Marvin’s Awesome iRacing App) and irFFB are a separate category that reshapes force feedback rather than analyzes laps; see MAIRA and irFFB for the wheel-oscillation and crash-protection caveats before you run one. See pedals for getting the brake inputs your traces depend on.

A review workflow that works

Run a 30 to 45 minute practice block. Then review the telemetry against a realistic reference, and jot two or three plain notes: “wider entry T7,” “earlier to throttle onto the back straight,” “trail brake deeper into the hairpin.” Fix one thing the next session. Reviewing the line and distance delta beats staring at the throttle and brake traces alone, and small written fixes stick better than a vague sense that you were slow. This is the same study loop the creators and further reading page describes: learn a fundamental, copy an onboard, then check your Garage 61 trace against it.